two speed vaccum troubles

[mikebeary]

Road testing 42 C.O.E. Having troubles staying put in high range. Any comments are welcome and thank you!!!

[jimTN]

Vac leak. Start at the front with the engine connections and go rearward. Had this happen on a F6 and worried with it a long time finally found a hose on the cowl that had hardened and nearly slid off the tube on the change valve. If I remember right the vac pod is spring loaded at the rear end so a vac leak causes it to jump out of high range.

[Kurt in NJ]

I had a 46 truck with 2 speed, learned to let up gas sometimes, that a burned valve reduced vacuum enough to make problems---that when the check valve gets gummed up it drops out quick under load ---and has been mentioned---vac leaks, when I put in a 49 merc it was like a miracle, the vacuum increase on hills helped

[Juergen]

I don't understand the vacuum leak problem. Vacuum is only used when shifting the Columbia and it should only be energized when you push in the clutch. Then the vacuum is applied. I would check the control where the vacuum is applied to either of the two lines to make sure no vacuum goes to the Columbia when the clutch is not depressed.

[Frank Miller]

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Originally Posted by Juergen

I don't understand the vacuum leak problem. Vacuum is only used when shifting the Columbia and it should only be energized when you push in the clutch. Then the vacuum is applied. I would check the control where the vacuum is applied to either of the two lines to make sure no vacuum goes to the Columbia when the clutch is not depressed.

This is not a columbia but a two speed truck rearend. Different animal.